The present invention refers to semiconductor devices with integrated coils and to a method for manufacturing semiconductor devices with integrated coils.
There exist semiconductor devices or chips capable of wireless radio frequency communication of data with outer devices. A known example of such radio frequency communicating semiconductor devices are so called Radio Frequency Identification (RFID) transponder, chips, labels or tags. An RFID label or tag is basically an RFID transponder that is embedded with an integrated circuit and an antenna. These wirelessly communicating RFID devices are usually equipped with integrated coils for providing a wireless data communication and/or wireless electrical power transmission from external sources to internal circuits of the semiconductor device.
The integrated coils can be used as a radiating element to wirelessly exchange data between the semiconductor device and outer devices. Furthermore, the integrated coils can be used for wireless electrical power transmission. This is achieved in an inductive manner, wherein an electromagnetic field generated by an external device causes an electric current in the coils integrated in the semiconductor device. The current produced by the integrated coils is then provided to the integrated circuits of the semiconductor device or other power consuming elements of the RFID chip or tag.
An RFID tag couples a radiating element, which may include a coil or antenna, to an integrated circuit without a physical conductor. The integrated circuit can be affixed to a substrate having the antenna in such a way that the circuit chip coil is inductively coupled to the antenna coil. When the RFID tag is excited via the antenna to an external electromagnetic field, the inductive coupling between the antenna and the external electromagnetic field can cause both signaling and power to couple from the antenna to the circuit chip coil without a physical conductor connecting the antenna to the RFID tag integrated circuit.
The integrated circuit of an RFID tag can be encrypted with a unique electronic product code that may identify the tagged item from any other item. When a tag comes within the range of an RFID reader, proprietary information can be passed on through an antenna to the reader, which then can feed the data to a central computer for processing.
There are active and passive RFID tags known. Passive RFID tags receive their power for operation from the external magnetic field and the current it induces into the integrated coil in the RFID tag. Active RFID tags may include internal power sources, e.g., batteries or accumulators to provide power supply for operating the power consuming elements of the RFID tag. Inductive RFID tags are powered by the magnetic field produced by a reader. The tag's antenna picks up magnetic energy, and the tag interacts with the reader. The tag then adjusts the magnetic field for retrieving and transmitting data back to the reader, and the reader directs that data to the host computer.
There exist two types of passive RFID tags, namely inductively coupled RFID tags, and capacitively coupled RFID tags. An inductively coupled RFID tag usually includes three parts, namely silicon microprocessor, metal coil, and encapsulating material. Silicon microprocessor chips differ in size, depending on their purpose.
A metal coil can be made, for instance, of copper or aluminum wire, wound into a circular pattern on a transponder, and acts as the tag's antenna. The RFID tag sends out signals to a reader, whereas the read distance depends on the size of the coil antenna. The elements of an RFID tag can be molded into an encapsulating material, e.g., some polymer material or glass that wraps around the chip and coil.
Capacitively coupled RFID tags have been manufactured in order to reduce the cost of radio-tag systems. These tags get rid of metal coil and utilize a little quantity of silicon to accomplish the same function as that of an inductively coupled tag. A capacitively coupled tag also has three components, namely silicon microprocessor, conductive carbon ink, and paper. A capacitively coupled tag can store a number of bits of information that would allow for a large amount of distinct numbers, and these numbers can be assigned to goods.
Conductive carbon ink is a special ink that can act as the tag's antenna. This ink is applied to the paper substrate by using usual printing techniques. A silicon chip can be affixed to printed carbon-ink electrodes on the back of a paper label, to create an inexpensive, disposable tag that can be integrated on conventional product labels.
In previous RFID semiconductor devices or chips integrated coils require substantial space on the chip and therefore cause large size of the RFID semiconductor devices and correspondingly additional costs to the production. In previous solutions, e.g., in a device known as SPT5 CT, the coils are implemented as concentric spirals by using metal lines in back-end-of-line (BEOL) applications. In such known devices the coils contribute to the required chip area with more than 50%.
Parts of a semiconductor device 1 with integrated coils 3 according to the state of the art is shown in FIG. 1. In this prior art semiconductor device 1 the chip area 2 has a square shape, and the integrated coils 3 are designed as a coil pair with circular shaped areas. The integrated coils 3 are contacted via electrical connections 4 to apply electrical voltage pulses to the coils for wireless data transmission or to gather inductively induced current from the coils 3 to provide power to the power requiring elements of the device. In this known device the integrated coils are arranged in one layer adjacent to each other and cover a bigger part, i.e. more than half of the chip area 2.